[Slick Moedee]

Don't believe the hype. The analysis is flawed for the conclusions they are trying to reach. A well written rebuttal to this article follows.

The Research Article “Impacts of Biodiversity Loss on Ocean Ecosystem Services”, (Worm et al., 3 November, p.787) projects that 100% of seafood-producing species stocks will collapse by 2048. The projection is inaccurate and overly pessimistic. This paper utilizes a dubious metric of stock collapse. It also fails to consider recent reports using more appropriate fish stock abundance data demonstrating that the proportion of overfished stocks has stabilized and is declining in the United States and elsewhere where increasingly effective fishery management is being pursued.

Worm et al. define “collapse” to occur when the current year’s catch is ≤10% of the highest observed in a stock’s time series. However, fish catch is rarely an adequate proxy for fish abundance, particularly for rebuilding stocks under management. A variety of biological, economic and social factors and management decisions determine catches; low catches may occur even when stocks are high (e.g., due to low fish prices or the effects of restrictive management practices), and vice versa. The inadequacy of Worm et al.’s abundance proxy is illustrated by the time series of data for Georges Bank haddock (Melanogrammus aeglefinus). The highest catch for haddock occurred in 1965 at 150,362 t (1). This catch occurred during a period of intense domestic and international fishing (1). In 2003 haddock catch was 12,576 t, or 8% of the time series maximum. Under the Worm et al. definition, the stock would be categorized as “collapsed” in 2003. However, stock assessment data (1) estimate the total magnitude of the spawning biomass in 2003 to be 91% of that in 1965. Comparing the estimate of spawning stock biomass in 2003 to the level producing maximum sustainable yield (MSY), the stock was not even being overfished in 2003 (2), never mind being “collapsed”. We therefore question the utility of a metric that could so utterly misrepresent the status of this and many other important USA fisheries.

Since adequate stock measures exist for only a portion of world fish stocks, this purported world-wide meta analysis required using data that represent the lowest common denominator of data – the total magnitude of the catch. However, if the catch ratio metric is so prone to misrepresentation of the true status of populations, as illustrated above, a synthesis of world fisheries based on these data is equally flawed. At the least, the authors should have conducted a calibration of their stock collapse metric with more complete stock abundance data available from the many worldwide sources where such data exist.

The extrapolation of their stock collapse metric to 100% by 2048 does not comport with the recent history of stock status, particularly in the United States. The National Marine Fisheries Service annually publishes a report to Congress on the status of fishery stocks (2). These data indicate that for the year 2005 about 26% of stocks were classified as “overfished”. For most stocks “overfished” status occurs when the population size drops below 50% of the population required to support MSY. Even under this more conservative definition of stock reduction, the proportion of stocks classified as “overfished” is actually declining slighly; in 2004 28% of stocks were so classified. Extrapolating a 2% decrease in the number of overfished stocks per year leads to a prediction that no stocks in USA jurisdiction would be overfished by the year 2018. However, such a meaningless projection does not incorporate a large number of complex factors, such as the differing life histories of species, impacts of variable ocean conditions on recruitment and the increasing effectiveness of management measures, all significant shortcomings of the prediction method and data contained in the Worm et al. paper as well.

Serious problems of overfishing and stock status are being addressed domestically under the Magnuson-Stevens Fishery Conservation and Management Act, and internationally through the many regional fishery management organizations (RFMOs). Admittedly, more needs to be done to improve governance institutions and control measures. This includes eliminating or reducing illegal, unregulated and unreported (IUU) fishing on the high seas, and increasing the effectiveness of RFMOs, for example in rebuilding depleted bluefin tuna, Thunnus thynnus, stocks in the Atlantic. Nevertheless, we believe the future situation regarding the condition of marine fish stocks is far less bleak than suggested by Worm et al., in the United States and elsewhere.

Steven Murawski1, Richard Methot2, Galen Tromble3

1Director of Scientific Programs and Chief Science Advisor, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Silver Spring, MD 20910, USA, 2Office of Science and Technology, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, WA 98112, USA, 3Chief, Domestic Fisheries Division, Office of Sustainable Fisheries, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Silver Spring, MD 20910, USA